UV curable pressure sensitive adhesive composition

ABSTRACT

A new UV curable pressure sensitive adhesive composition, which comprises in weight percent: about 0.1% to about 15% of a photoinitiator agent, about 10% to about 80% of a polyurethane resin with a pendent acrylate functionality, zero to about 70% by of an acrylate monomer, about 0.1% to about 25% by weight of a an acrylated polybutadiene component, and zero to about 50% by weight of a tackifier agent.

This is a continuation of U.S. Pat. application Ser. No. 08/349.687,filed Dec. 5, 1994, now abandoned.

BACKGROUND OF THE INVENTION

This invention broadly relates to a new UV curable pressure sensitiveadhesive composition and method of using same. By the term "UV curable"as used herein it is meant curable with ultraviolet radiation.

Pressure sensitive adhesives are materials that form a bond with verylight pressure. The cured adhesive is neither solid nor liquid, butrather is a viscoelastic material that is usually quite tacky. Whilepressure sensitive adhesives are available as 100% solids for hot meltapplications, and as water-based emulsion acrylic systems, the majorityof the approximately 500 million dry pound domestic market in the U.S.A.are solvent based products. UV curable pressure sensitive adhesivesrepresent only a few percent of the market, in large part because of theproblem with their historical poor high temperature properties. In thepast it has been thought that a UV curable pressure sensitive adhesiveexhibiting acceptable high temperature and environmental performancecharacteristics could capture a large percent of the market share forpressure sensitive adhesives. Also in the past, there have been some UVcurable pressure sensitive adhesives which included a polyurethaneresin; however, they did not have the necessary integrity or performancecharacteristics at temperatures above approximately 130°-140° F., andthey also exhibited poor humidity resistance.

While UV curable pressure sensitive adhesives do not currently command asignificant market share, the interest remains high in this type ofpressure sensitive adhesive technology. Various other companies andindividuals have worked on solving the problems associated with thistechnology; however, such other parties have not been able to developsatisfactory products which would be usable and worthwhile in industry.

Pressure sensitive adhesives (PSAs) are tacky substances normally oroften placed on backing materials which, when brought in contact with asurface under light contact exhibit sufficient cohesiveness as to resistpeeling away from that surface. Classic examples of the usage ofpressure sensitive adhesives are tapes, bandaids, and labels.

The chemistry of pressure sensitive adhesives can be roughly sub-dividedinto three large groups: 1) solvent-based adhesives, 2) water-basedadhesives, and 3) radiation cured adhesives.

Solvent-based adhesives are typically ultra-high molecular weight (Mw),soft polymers (low Tg) dissolved in solvent; when applied to a backingmaterial, they provide tack or stickiness of the backing material to acontacted surface. While the chemistry involved is complex, involvingdifferent chemical polymers and block copolymer polymerizations, it canbe reduced to one generic classification--thermoplastic polymers (TPs).Thermoplastic polymers on this theme are large, low Tg molecules whichentangle on a molecular level, giving tack and strength at roomtemperature. (Tg means glass transition temperature). The liability ofTPs is high-temperature strength. Typically at temperatures exceeding120° F., all strength is lost as the polymers adopt a parallelarrangement to force lines when stressed. Higher Mw polymers, ingeneral, behave better at elevated temperatures, but usually requirehigher VOC solutions, and still the integrity at temperatures ofapproximately 140° F. or higher is suspect. VOC stands for volatileorganic compound(s).

Water-based PSAs can be considered as nothing more than variants on thethermoplastic polymer theme. Again, low Tg, ultra-high Mw polymers aresuspended in solution (water); film formation and chain entanglementthen occur when the latex particles coalesce with drying.

The advantages of water-based PSAs are the abatement of air pollution(low VOC) and generally enhanced oxidation resistance of the final film.The liability of this chemistry is identical to its solvent-basedcounterpart;--high-temperature strength. To achieve better strength athigh temperatures, higher Tg polymers are sometimes used and thetrade-off is always tack;--the end-product does not efficiently grabcontacting surfaces. Tack and high-temperature strength are the featureswhich are diametrically opposed in TP chemistry.

Radiation-cured PSAs can be subdivided into electron beam (EB) films andultraviolet curable (UV) films. The chemistry is similar in that uncuredmixtures of unsaturated polymerizable compounds are irradiated in bothinstances, but EB films have dominated the past high-temperature market.Electron beam adhesives are usually formed by applying solutions (VOCs)of high Mw polymers with a small amount of double bonds to the substratethey will be used on, and then exposing the resultant film to a high-intensity electron gun. The electrons secondarily crosslink the alreadyhigh Mw material giving a thermoset nature to the end-product. Finalfilm Tg is not dramatically enhanced; Mw of the polymers approachesinfinity, and therefore, the result is a film which has strength atelevated temperatures, up to 200° F., and tack at room temperature. EBfilms are satisfactory for some applications, but solutions must be usedto apply the initially high MW prepolymers (e.g., detrimental VOC's),and the electron beam process is slow cumbersome, and costly. An EB guncosts approximately one million dollars.

UV cure is attractive, therefore, because it involves 100% convertiblematerial with a simpler and more economical manufacturing process. Up tothis point combinations of Mw oligomers have had to be used forapplication purposes; high Mw prepolymers are much higher in viscosityand, therefore, require a solvent. The problem in using low Mw oligomersis that it has been virtually impossible to generate high Mwend-products in the curing time frames usually encountered. The resultis a lower overall Mw film which obtains its integrity via theincomplete polymerization of higher Tg starting materials. While thiscan give decent room temperature tack and cohesion, high-temperaturestrength is severely compromised. In the past UV-curable PSAs have hadvirtually no strength at 130° F.

Accordingly it is a primary object of the present invention to provide anew UV curable pressure sensitive adhesive composition, and method ofusing same.

Another object of the present invention is to provide a new UV curablepressure sensitive adhesive composition which exhibits good performancecharacteristics at temperatures in the range of approximately 130°-140°F. or higher.

Another object of the present invention is to provide a new UV curablepressure sensitive adhesive composition which exhibits excellentproperties in terms of humidity resistance and high temperatureperformance.

Another object of the present invention is to provide a novel pressuresensitive adhesive composition which is environmentally friendly andeconomical to produce.

Other objects, features and advantages of the present invention willbecome apparent from the subsequent description and the appended claims.

SUMMARY OF THE INVENTION

While it is not fully or completely understood as to why the inventiondescribed herein produces such good results and highly desirableperformance characteristics, it has been found that the UV curablepressure sensitive adhesive composition now to be described provides ahighly advantageous new pressure sensitive adhesive.

Briefly stated, the invention concerns a new UV curable pressuresensitive adhesive composition, comprising in weight percent: (a) about0.1% to about 15% photoinitiator agent, (b) about 10% to about 80% of apolyurethane resin with a pendent acrylate functionality and having amolecular weight within the range of about 500 to about 2,000,000, (c)about zero to about 70% of an acrylate monomer having a molecular weightwithin the range of about 50 to about 5,000, (d) about 0.1% to about 25%of an acrylated polybutadiene having a molecular weight within the rangeof about 500 to about 500,000, and (e) about zero to about 50% of atackifier agent. The invention also involves a method of using theadhesive composition comprising the steps of: applying said adhesivecomposition to a substrate surface, subjecting said adhesive compositionto ultraviolet radiation, positioning an object in contact with saidadhesive composition to adhere said object in position on said substratesurface.

The acrylated polybutadiene, as shown in the later examples herein, is amaterial which is commercially available from Ricon Resins, Inc. ofGrand Junction, Colo.

DESCRIPTION OF BEST MODE AND PREFERRED EMBODIMENTS

The photoinitiator agent used in the composition of the invention shouldpreferably be of the free radical photoinitiator type. Typicalphotoinitiator agents that may be used are: diethoxyacetophenone,benzophenone, IRGACURE 651, or DAROCUR 1173. There are numerous otherphotoinitiator agents of a type similar to those just described, whichcan be used, and which will be apparent to those skilled in the art.Broadly stated the photoinitiator agent should be present within thecomposition within the broad range of about 0.1% to about 15% by weightof the composition, and preferably within the range of about 1/2% toabout 10% by weight of the composition. Best results are obtained whenthe photoinitiator agent is present within the range of about 1% toabout 6% by weight of the composition.

The polyurethane resin component of the composition should be apolyurethane resin which has a pendent acrylate functionality. It hasbeen found that this polyurethane resin should have a molecular weightwithin the broad range of about 500 up to about 2,000,000, andpreferably its molecular weight should be within the range of about1,000 to about 500,000. Best results are obtained using a polyurethaneresin having a molecular weight within the range of about 2,000 to about30,000. The polyurethane resin should be present in the compositionwithin the broad range of about 10% to about 80% by weight of thecomposition, and preferably within the range of about 20% to about 50%by weight. Best results are obtained when the polyurethane resincomponent is present within the range of about 20% to about 45% byweight of the composition. Suitable materials which can be used as thispolyurethane resin are: Purelast 169V, Purelast 176A, Purelast 169,Purelast 166, and Purelast 165 available from Polymer Systems Co.(Orlando, Fla.)!, Ebecryl 230 (Radcure Co., Louisville, Ky.), SartomerCN966, and Sartomer CN965 (Sartomer Co., Exton, Pa.).

The acrylate monomer for use in the composition is a monomer which interreacts with the polyurethane resin. This acrylate monomer should have amolecular weight within the broad range of about 50 to about 5,000, andpreferably its molecular weight is within the range of about 100 toabout 2,000. Best results are obtained using an acrylate monomer havinga molecular weight within the range of about 120 to about 500. Theacrylate monomer may be present in the composition, broadly stated,within the range of about zero to about 70% by weight of thecomposition, and preferably it is present within the range of about 10%to about 55% by weight of the composition. However, in some instancesthe acrylate monomer may be present at a low level of only about 1% byweight. Best results are obtained when the acrylate monomer is presentwithin the range of about 15% to about 50% by weight of the composition.Typical acrylate monomers which may be used in the composition areisobornyl acrylate (IBOA) monomer or the Sartomer acrylate monomerSR-339. The acrylate monomer can be described as being selected from atleast one member of the group consisting of methacrylate monomer, anethyl acrylate monomer, an isobornyl acrylate monomer, a cyclohexylacrylate monomer, a butyl acrylate monomer, a propyl acrylate monomer, apentyl acrylate monomer, a hexyl acrylate monomer, and a glycidylacrylate monomer.

The acrylated polybutadiene component of the composition is also a veryimportant constituent in properly preparing the pressure sensitiveadhesive described herein. It has been discovered that the addition of aspecified amount of this acrylated polybutadiene material (which shouldnormally be obtained or prepared by a Ziegler Natta polymerization)enables the unique performance characteristics that are obtained withthis invention in combination with the other important materialsdescribed. This polybutadiene material used in the composition should,broadly stated, have a molecular weight within the range of about 500 toabout 500,000, and preferably within the range of about 1,000 to about70,000. Best results are obtained when it has a molecular weight withinthe range of about 4,000 to about 6,000. This polybutadiene material asdescribed herein should be present in the composition within the broadrange of about 0.1% to about 25% by weight of the composition, andpreferably within the range of about 1/2% to about 10% by weight. Bestresults are obtained when the acrylated polybutadiene material ispresent within the range of about 1% to about 5% of the composition.Maleic anhydride adducts of acrylated polybutadiene are also fullyacceptable in this invention.

The tackifier agent used in the composition may suitably be any one of anumber of different tackifiers such as rosins, rosins esters, tall oilrosins, pentaerythritol ester, and other commercially availablealiphatic and aromatic tackifier materials. The tackifier agent, broadlystated, may be present in the composition within the range of zero toabout 50% by weight of the composition, and preferably it is presentwithin the range of about 0.1% to about 35% by weight of thecomposition. Best results are obtained when the tackifier agent ispresent within the range of about 5% to about 25% by weight of thecomposition.

Other optional additive materials may also be used in the composition ofthe invention, which optional materials may be present in relativelyminor amounts that is, from about 0.05% to about 10% by weight of thecomposition. Such other optional materials that may be used in thecomposition are: pigments, rheology modifiers, flow aids, antioxidants,and/or bubble release agents.

DESCRIPTION OF THE DRAWING FIGURES

The drawing illustrations of FIGS. 1, 2 and 3 present in graphicalrepresentations the performance characteristics obtained with theadhesive compositions of this invention.

The FIG. 1 graph shows the markedly improved results obtained in termsof heat resistance using the UV curable pressure sensitive adhesive inaccordance with Example 1. In FIG. 1 a prior art PSA adhesivecomposition is referred to as the PSA control. The adhesive compositionin accordance with the Example 1 of this invention is designatedML-2525 1. FIG. 1 illustrates that the adhesive composition of theinvention gave excellent resistance when tested for a time period of 15hours continuously from 100° F. out to approximately 225° F.; whereas,the PSA control sample (the prior art PSA composition) markedly fell offin terms of heat resistance at approximately 125° F.-130° F. The testprocedures for the FIG. 1 graph were carried out in overlapping shearmode, with a 1000 gram weight being attached to the shearing specimens,which were two tape- like substrates overlapped and adhered togetherwith the PSA at an approximately one square inch overlap area. Theadhesive was coated on the overlapping shear samples at a thickness ofapproximately 4 mils on all samples tested in FIG. 1.

The FIG. 2 graph illustrates the improved performance of the adhesivecomposition of the invention in terms of tack stability. In FIG. 2, theleft hand side of the graph or chart is given in pounds per linear inch(PLI), versus time (n in weeks) on the lower coordinate. In the testingof FIG. 2 two tape-like substrates are adhered together using first apressure sensitive adhesive composition of the prior art (PSA control),and the two substrates are pulled apart at a 180° pull angle, with thepull speed being approximately 1/2 inch per minute; and, the test isconducted at room temperature. The same procedure was used for testingthe Example 1 composition of the invention, which is designated ML-25250in FIG. 2.

In the graphical representation of FIG. 3, the marked improvement inhumidity resistance characteristics for the composition of the inventionis demonstrated. In FIG. 3 the test samples were again examined underlap shear mode, which indicates two tape-like substrates being adheredtogether with approximately a 1 square inch overlap at the lap sheararea; and, a 1000 gram weight is hung off of the lower substrate until afailure occurs, that is until the two substrates separate throughfailure at the 1 square inch overlap area. The applied thickness ofadhesive coating for both the prior art composition and the compositionof the invention (Ex. 1) was approximately a 4 mil thickness.

For all of the tests conducted in FIG. 3 the humidity conditionsthroughout the test time frame were 100° F. and 100% relative humidity(non condensing) within the testing chamber.

In the FIG. 3 graphical representation, the improvement of the inventivecomposition is shown in terms of its markedly improved humidityresistance. In FIG. 3 the number of hours to failure is shown on theleft hand side of the graph, and the test was terminated after 24 hours.As seen in the first test conducted on the left hand part of FIG. 3,indicated by columns 1A and columns 1B, the sample test in column 1Awhich utilized the Example 1 composition of this invention, performssatisfactorily throughout the entire 24 hour test period, at which timethe test was terminated. Whereas the sample 1B material which was aprior art pressure sensitive adhesive control of the UV curable type,failed after approximately one hour of testing. This test as indicatedby the columns 1A and 1B in FIG. 3, utilized a lap shear mode of testingwherein two approximately 1 inch wide tape substrates were coated at theoverlap area (amounting to approximately 1 square inch of overlapsurface) with an applied 4 mil thickness of the pertinent adhesivecoating composition being applied. The tests in columns 1A and 1B werebetween two untreated polyester substrates.

In the test demonstrated by column 2A and column 2B in FIG. 3, the sametype of test was conducted; however, the two substrates were anuntreated polyester tape substrate applied to a stainless steelsubstrate with the same type of lap shear overlap mode being used, witha 1000 gram weight being hung from the adhered together substrates inorder to conduct the test.

In the FIG. 3 test results shown by column 2A and column 2B it is seenagain that the sample using the adhesive of Example 1 of this inventionperforms satisfactorily throughout the entire 24 hour test period,whereas the UV curable pressure sensitive adhesive control sample failedat approximately one hours time.

In the test conducted as shown by column 3A and column 3B in FIG. 3, thetwo substrates adhered together in the lap shear mode were a treatedpolyester substrate to a second treated polyester substrate, with anapproximately 1 square inch overlap area being adhered together withapproximately a 4 mil thick applied coating of the pertinent adhesive.As shown in column 3A the adhesive in accordance with Example 1 of theinvention performs satisfactorily throughout the entire 24 hour testperiod, whereas the pressure sensitive adhesive control of the prior artfailed after approximately one hours time.

In the last test conducted in FIG. 3, as shown by columns 4A and 4B thetwo substrates adhered together in the lap shear mode were a treatedpolyester substrate to a steel substrate, using an approximately 1square inch adhesive overlap area, with a 1000 gram weight being hungfrom the lower substrate. Again the sample using the adhesive inaccordance with Example 1 of the invention performed satisfactorilythroughout the entire 24 hour test period, whereas the sample using theUV curable pressure sensitive adhesive composition of the prior artfailed after approximately one hour's time.

In order to further illustrate the invention, the following examples areprovided. It is to be understood, however, that the examples areincluded for illustrative purposes and are not intended to be limitingof the scope of the invention as set forth in the subjoined claims.

EXAMPLE 1

    ______________________________________                                        Parts by Weight                                                               ______________________________________                                        Purelast 169V      29.60  Urethane Resin                                      Purelast 176A      3.52   Urethane Resin                                      Ricacryl Lac       2.00   acrylated polybutadiene                             (available from Ricon Resins, Inc.                                            Grand Junction, Colo.)                                                        Sylvatac 25N       4.23   Tackifier                                           Norcote 02-065     1.15   Flow Aid                                            IBOA Monomer       28.11  Acrylate Monomer                                    (available from Radcure Co,                                                                             (formula wgt. = 208)                                Louisville, Ky.)                                                              SR-339 Monomer     12.62  Acrylate Monomer                                    (available from           (formula wgt. = 192)                                Sartomer Co.)                                                                 Foral-105          17.50  Tackifier                                           (Hercules, Inc., Wilmington, Del.)                                            DEAP               0.36   Initiator                                           (diethoxyacetophenone)                                                        Benzophenone       1.08   Initiator                                           (Upjohn Co.)              (M.W. = 182.21)                                     Irgacure 651       1.62   Initiator                                           (Ciba-Geigy Corp.)                                                            Darocur 1173       0.91   Initiator                                           (EM Industries, Inc. Hawthorne, N.Y.)                                         ______________________________________                                    

The Riacryl Lac™ material is commercially available from Ricon Resins,Inc.(Grand Junction, Colo.) and is known as an acrylated polybutadiene;and it has the following characteristics:

    ______________________________________                                        Solvent              None                                                     Nonvolatile Matter (w/w)                                                                           98.0%                                                    Microstructure       25% ± 5% 1,2-vinyl                                    Molecular Weight                                                              (M).sub.n            5000                                                     (M).sub.w            21000                                                    Physical State       Viscous Liquid                                           Brookfield Viscosity (25° C.)                                                               9500 cP                                                  Specific Gravity     0.9                                                      Bulk Density         7.6 lbs/gal                                              Flash Point (Tag Closed Cup)                                                                       N/A                                                      Acid Number          2.5 ppt KOH                                              Gardner Color        9 Maximum                                                Inherent Viscosity   0.133 typical --.                                        (6 g real resin/100 ml toluene)                                               ______________________________________                                    

    ______________________________________                                                 Examples (In Parts By Weight)                                        Component  No. 2    No. 3   No. 4 No. 5  No. 6                                ______________________________________                                        Purelast 169V                                                                            35.90    40.90   16.01 26.90  26.90                                Purelast 176A                                                                            5.52     7.52    7.52  3.52   3.52                                 Ricacryl Lac                                                                             2.14     2.00    2.00  2.00   2.00                                 Sylvatac 25N                                                                             4.23     4.23    4.23  4.23   4.23                                 Norcote 02-065                                                                           1.15     1.15    1.15  1.15   1.15                                 IBOA Monomer                                                                             19.00    12.11   25.00 28.11  28.11                                SR-339     10.62    10.62   9.62  12.62  12.62                                Foral 105  17.50    17.50   30.50 17.50  17.50                                DEAP       0.36     0.36    0.36  1.08   1.62                                 Benzophenone                                                                             1.08     1.08    1.08  0.36   0.36                                 Irgacure 651                                                                             1.62     1.62    1.62  1.62   1.08                                 Darocure 1173                                                                            0.91     0.91    0.91  0.91   0.91                                 ______________________________________                                                 Examples (In Parts By Weight)                                        Component  No. 7    No. 8   No. 9 No. 10 No. 11                               ______________________________________                                        Purelast 169V                                                                            26.90    26.90   26.90 26.90  26.90                                Purelast 176A                                                                            8.52     8.52    10.52 3.52   3.52                                 Ricacryl Lac                                                                             2.00     2.00    2.00  2.00   2.00                                 Sylvatac 25N                                                                             10.23    10.23   12.43 4.23   4.23                                 Norcote 02-065                                                                           1.15     1.15    1.15  1.15   1.15                                 IBOA Monomer                                                                             28.11    23.11   21.11 28.11  1.11                                 SR-339     12.62    6.62    4.62  1.62   39.62                                Foral 105  6.50     17.50   17.50 28.50  17.50                                DEAP       0.36     0.36    0.36  0.36   0.36                                 Benzophenone                                                                             1.08     1.08    1.08  1.08   1.08                                 Irgacure 651                                                                             1.62     1.62    1.62  1.62   1.62                                 Darocure 1173                                                                            0.91     0.91    0.91  0.91   0.91                                 ______________________________________                                                 Examples (In Parts By Weight)                                        Component  No. 12   No. 13  No. 14                                                                              No. 15 No. 16                               ______________________________________                                        PURELAST 169V                                                                            26.90    26.90   26.90 24.90  16.90                                PURELAST 176A                                                                            3.52     3.52    3.52  3.52   8.52                                 RICACRYL LAC                                                                             6.00     2.00    2.00  4.00   6.00                                 SYLVATAC 25N                                                                             4.23     4.23    4.23  4.23   5.23                                 NORCOTE 02-065                                                                           1.15     1.15    1.15  1.15   1.15                                 IBOA Monomer                                                                             24.11    28.11   28.11 28.11  28.11                                SR-339     12.62    12.62   12.62 10.62  10.62                                FORAL 105  17.50    17.50   17.50 17.50  17.50                                DEAP       0.36     0.16    0.36  0.36   0.36                                 Benzophenone                                                                             1.08     1.28    1.78  1.78   1.78                                 IRGACURE 651                                                                             1.62     1.62    1.62  1.62   1.62                                 DAROCURE 1173                                                                            0.91     0.91    0.41  0.41   0.41                                 ______________________________________                                    

This invention allows efficient cross-linking of high Tg oligomers orpolymers by coupling the polymerization mechanism to an extremely low Tgvinyl-terminated rubber. The rubber addition is unique and importantbecause it crosslinks to the matrix simultaneously acting as aplasticizing resin and providing tack without sacrificing elevatedtemperature strength. Rubbers, in general, do not efficiently UV cureand act only as tackifiers/plasticizers in acrylate-based mixtures. Thechosen rubber is a unique class of acrylated polybutadienes obtainedfrom a Ziegler Natta polymerization. The pendant 1, 2-structure alongthe back bone is believed to polymerize into a growing free radicalinitiated moiety. All molecular weights referred to in this disclosureare number average molecular weights (M)_(n).

While it will be apparent that the preferred embodiments of theinvention disclosed are well calculated to fulfill the objects,benefits, and/or advantages of the invention, it will be appreciatedthat the invention is susceptible to modification, variation and changewithout departing from the proper scope or fair meaning of the subjoinedclaims.

What is claimed is:
 1. A method comprising the steps of:applying a UVcurable pressure sensitive adhesive composition, comprising in weightpercent: (a) about 0.5% to about 10% photoinitiator agent, (b) about 20%to about 50% of a polyurethane resin with a pendent acrylatefunctionality, and having a molecular weight (M_(N)) within the range ofabout 500 to about 2.000.000, (c) about 10% to about 55% of an acrylatemonomer, having a molecular weight within the range of about 50 to about5.000, (d) about 1/2% to about 10% of acrylated polybutadiene materialhaving a molecular weight (M_(N)) within the range of about 4000 toabout 6000, and (e) about 0.1% to about 35% of a tackifier agent, to asubstrate surface, subjecting said adhesive composition to ultravioletradiation, positioning an object in contact with said adhesivecomposition to adhere said object in position on said substrate surface.2. The method of claim 1 wherein,said polyurethane resin has a molecularweight (M_(N)) within the range of about 1,000 to about 500,000, saidacrylate monomer has a molecular weight within the range of about 100 toabout 2,000.
 3. The method of claim 2 wherein,(a) said photoinitiatoragent is present from about 1.0% to about 6%, (b) said polyurethaneresin is present from about 20% to about 45%, (c) said acrylate monomeris present from about 15% to about 50%, (d) said polybutadiene materialis present from about 1% to about 5%, (e) said tackifier agent ispresent from about 5% to about 25%.
 4. The method of claim 3wherein,said polyurethane resin has a molecular weight (M_(N)) withinthe range of about 2,000 to about 30,000, said acrylate monomer has amolecular weight within the range of about 120 to about
 500. 5. Themethod of claim 2 wherein,said photoinitiator agent is a free radicalphotoinitiator type, said acrylate monomer is selected from at least onemember of the group consisting of a methacrylate monomer, an ethylacrylate monomer, an isobornyl acrylate monomer, a cyclohexyl acrylatemonomer, a butyl acrylate monomer, a propyl acrylate monomer, a pentylacrylate monomer, a hexyl acrylate monomer, and a glycidyl acrylatemonomer.
 6. The method of claim 5 wherein,there is also included a minoramount of optional additive materials such as pigments, rheologymodifiers, flow aids, antioxidants, or a bubble release agent.
 7. Themethod of claim 5 wherein,there is also included a minor amount ofoptional additive materials such as pigments, rheology modifiers, flowaids, antioxidants, or a bubble release agent, and said tackifier agentis selected from at least one member of the group consisting of rosins,rosin esters, tall oil rosins, and pentaerythritol ester.